The Clinical Trials Core will conduct phase I and II vaccine trials initiated by CHAVI in a rapid, efficient and coordinated manner. The Core will provide the following functions: (1) design of phase I and II clinical protocols; (2) recruit and retain volunteer subject populations; (3) assess safety and immunogenicity of vaccine candidates; (4) collect data and clinical samples; (5) provide quality control; (6) analyze data. The Clinical Trials Core will interact at early stages in the development of vaccine candidates through membership in Vaccine Discovery Teams, and through active interaction in the development process leading up to and involving clinical trials. In the U.S., the Core will carry out vaccine trials at the clinical studies facility based at Brigham and Women's Hospital, which is the site used for the Harvard HIV Vaccine Trials Unit (HVTU). Studies will be conducted by a highly experienced vaccine trials team led by Dr. Raphael Dolin, which has had a high level of performance in HVTN studies. The Clinical Trials Core will also work closely with the CHAVI Acute HIV Infection Network described in Core B to prepare, train, and coordinate those clinical sites to conduct phase I and II vaccine trials as needed. The Clinical Trials Core will also assist the investigators in Core B to provide support for the conduct of acute HIV infection studies as needed, particularly during the first year of the award. The Clinical Trials Core will have the capability to conduct two phase I or one phase II study annually, likely beginning in year 2 of the award. The Core will closely coordinate its activities with those of the HIV Vaccine Trials Network (HVTN) to take advantage of its infrastructure and data analysis capabilities and to expand the size of the clinical trials as warranted.